Post on 12-Sep-2020
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#WWDC14
Advanced iOS Application Architecture and Patterns
Session 229 Andy Matuschak iOS Apps and Frameworks
Frameworks
!
Colin Barrett iOS Apps and Frameworks
Software Architecture
Software Architecture…?
Five Things to Never Do in Your AppIt’s software architecture! We promise!
1. Don’t ever use class names explicitly
2. Avoid bare C functions with singletons
3. Why are you reading this?
4. It’s a joke; these are bad ideas
5. Or maybe just dogmatic ideas
“You Ain’t Gonna Need It!”
“You Ain’t Gonna Need It!”“Big Design Up Front.”
vs.
architecturetaste
ability
abilityarchitecture
taste
Insight, not dogma
Insight, not dogmaWhy, not how
Design Information Flow1
Define Clear Responsibilities2
Simplify with Immutability3
Simplify with Immutability3
Design information flow1
Define clear responsibilities2
Simplify with immutability3
Design information flow1
Define clear responsibilities2
Simplify with immutability3
Where Is “Truth”?
DemoWhere is truth?
photo tap action text view focus action
drawer view exists?
photo tap action text view focus action
drawer view exists?
drawer expanded?
photo tap action text view focus action
drawer view exists?
drawer expanded?
photo tap action text view focus action
drawer view exists?
drawer expanded?
Where Is “Truth”?
photo tap action text view focus actiondrawer view exists?
drawer expanded?
Where Is “Truth”?
photo tap action text view focus actiondrawer view exists?
drawer expanded?
drawer view exists?
drawer expanded?
derived value
truthTruth
Derived values
vs.
DemoTruth vs. derived values
text view value character count
model
Derived Values
derived value
input A input B
Derived Values
Compute from inputs
derived value
input A input B
Derived Values
Compute from inputs
Recompute when inputs change
derived value
input A input B
Derived Values
Compute from inputs
Recompute when inputs change
…Like a cache!
derived value
input A input B
original data
cached data
original data
cached data
staleness
original data
cached data
staleness
original data
cached data
staleness
original data
cached data
staleness
original data
cached data
staleness efficiency
original data
cached data
staleness efficiency
truth
derived values
truth
derived values
staleness efficiency
text view value character count
model
text view value character count
model
defines
text view value character count
model
definesinvalidates
text view value character count
model
definesinvalidates
defines
text view value
character count
model
definesinvalidates defines
invalidates
text view value
character count
model
definesinvalidates
invalidates
defines
text view value character count
model
definesinvalidates
defines
text view value character count
model
definesinvalidates
definesinvalidates
Truth vs. Derived Values
character count
model
text view value
model
text view value
text view value
model
model
text view value
Creating New Truth
derived value
truth
DemoCreating new truth
text view value character count
model
text view value character count
model
text view value character count
model
original model
entry viewing controller
entry editing controller
Creating New Truth
text view value character count
model
original model
entry viewing controller
entry editing controller
Design Information Flow1
Design Information Flow
Where is “truth”?
1
Design Information Flow
Where is “truth”?
Truth vs. derived values
1
Design Information Flow
Where is “truth”?
Truth vs. derived values
Creating new truth
1
Simplify with immutability3
Design information flow1
Define clear responsibilities2
Username Johny Appleseed ?
Password ••••••••••••••
ConfirmPassword ••••••••••••••
Email johnnyappleseed@icloud.com
Sign In
Invalid username or password!
Sign InForgot password?
Validation
Validation
Check if valid
If all valid
Enable sign-up button
For each text field
Validation
For each text field
Check if valid
If all valid
Enable sign-up button
Validation
For each text field
Check if valid
If all valid
Enable sign-up button
Validation
Check username field
Check first password field
Check second password field equals first
Check email address field
For each text field
Check if valid
If all valid
Enable sign-up button
Validation
Check username field
Check first password field
Check second password field equals first
Check email address field
For each text field
Check if valid
If all valid
Enable sign-up button
Validation
Check username field
Check first password field
Check second password field equals first
Check email address field
Validation
Check username field
Check first password field
Check second password field equals first
Check email address field
Validation
Create a regular expression
Find matches in username
If have any matches
Username is valid
Check username field
Check first password field
Check second password field equals first
Check email address fieldOtherwise
Decorate text field
ValidationHandling nil
For each text field
Check if valid
If all valid
Enable sign-up button
ValidationHandling nil
For each text field
Check if valid
If all valid
Enable sign-up button
ValidationHandling nil
For each text field
Check if valid
If all valid
Enable sign-up button
ValidationHandling nil
If nil
Leave text field alone
For each text field
Check if valid
If all valid
Enable sign-up button
ValidationHandling nil
For each text field
Check if valid
If all valid
Enable sign-up button
ValidationHandling nil
For each text field
Check if valid
If all valid
Enable sign-up button
ValidationHandling nil
If any nil
Leave sign-up button disabled
For each text field
Check if valid
If all valid
Enable sign-up button
Validation
Create a regular expression
Find matches in username
If have any matches
Username is valid
Check username field
Check first password field
Check second password field equals first
Check email address fieldOtherwise
Decorate text field
Validation
NSString *username = [self.usernameField text]; NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@“[a-zA-Z0-9_]{6,}” options:0 error:nil]; NSRange result = [regex rangeOfFirstMatchInString:username options:NSMatchingAnchored range:NSMakeRange(0, [username length])]; if (username && result.location == NSNotFound) { allValid = NO; [self.usernameField setBackgroundColor:[UIColor redColor]]; } else { if (!username) { anyNil = YES; } [self.usernameField setBackgroundColor:[UIColor whiteColor]]]; }
Validation
NSString *username = [self.usernameField text]; NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@“[a-zA-Z0-9_]{6,}” options:0 error:nil]; NSRange result = [regex rangeOfFirstMatchInString:username options:NSMatchingAnchored range:NSMakeRange(0, [username length])]; if (username && result.location == NSNotFound) { allValid = NO; [self.usernameField setBackgroundColor:[UIColor redColor]]; } else { if (!username) { anyNil = YES; } [self.usernameField setBackgroundColor:[UIColor whiteColor]]]; }
View Controller A
Text Field
Text Field
Text Field
Button
View Controller A
Text Field
Text Field
Text Field
ButtonValidation
View Controller A
Text Field
Text Field
Text Field
ButtonValidation
View Controller B
Text Field
Text Field
ButtonValidation
View Controller B
Text Field
Text Field
Button
View Controller A
Text Field
Text Field
Text Field
Button
ValidationValidation
Validation
Validation
What is validation?
Validation
What is validation? Inputs Outputs
Validation
What is validation?• Given an input value
Inputs Outputs
inputValue: Any
Validation
What is validation?• Given an input value
• Is input value valid?
Inputs Outputs
inputValue: Any isValid: Bool
Validation
What is validation?• Given an input value
• Is input value valid?
• If not, why not?
Inputs Outputs
inputValue: Any isValid: Bool
error: NSError?
ValidationFoundations
ValidationFoundations
protocol Validator { validateWithError(error: NSErrorPointer) -> Bool }
ValidationFoundations
protocol Validator { validateWithError(error: NSErrorPointer) -> Bool }
Definition of “input” left open to interpretation
ValidationFoundations
protocol Validator { validateWithError(error: NSErrorPointer) -> Bool }
Definition of “input” left open to interpretation
Build larger validators out of smaller ones
ValidationFoundations
protocol Validator { validateWithError(error: NSErrorPointer) -> Bool }
Definition of “input” left open to interpretation
Build larger validators out of smaller ones
Composition
ValidationFoundations
protocol Validator { validateWithError(error: NSErrorPointer) -> Bool }
Definition of “input” left open to interpretation
Build larger validators out of smaller ones
Composition
Works fine in Objective-C, too
ValidationUsernames
ValidationUsernames
class UsernameValidator: Validator { var input: NSString? func validateWithError(error: NSErrorPointer) -> Bool { let regex = NSRegularExpression(pattern: ...) ... }}
ValidationPasswords
ValidationPasswords
class PasswordValidator: Validator { var input: NSString? ...}
ValidationPasswords
class PasswordValidator: Validator { var input: NSString? ...}
Represents the validity of a single password field
ValidationPasswords
class PasswordValidator: Validator { var input: NSString? ...}
Represents the validity of a single password fieldclass SetPasswordValidator: Validator { let firstPasswordValidator = PasswordValidator() let secondPasswordValidator = PasswordValidator() ...}
ValidationPasswords
class PasswordValidator: Validator { var input: NSString? ...}
Represents the validity of a single password fieldclass SetPasswordValidator: Validator { let firstPasswordValidator = PasswordValidator() let secondPasswordValidator = PasswordValidator() ...}
Represents two password fields that must match in value
ValidationOverall form
ValidationOverall form
class SignUpValidator: Validator { let usernameValidator = UsernameValidator() let setPasswordValidator = SetPasswordValidator() let emailAddressValidator = EmailAddressValidator() ...}
ValidationOverall form
class SignUpValidator: Validator { let usernameValidator = UsernameValidator() let setPasswordValidator = SetPasswordValidator() let emailAddressValidator = EmailAddressValidator() ...}
Represents the validity of the entire form
ValidationOverall form
class SignUpValidator: Validator { let usernameValidator = UsernameValidator() let setPasswordValidator = SetPasswordValidator() let emailAddressValidator = EmailAddressValidator() ...}
Represents the validity of the entire form
Behavior of nil
ValidationOverall form
class SignUpValidator: Validator { let usernameValidator = UsernameValidator() let setPasswordValidator = SetPasswordValidator() let emailAddressValidator = EmailAddressValidator() ...}
Represents the validity of the entire form
Behavior of nil• Most validators allow nil
ValidationOverall form
class SignUpValidator: Validator { let usernameValidator = UsernameValidator() let setPasswordValidator = SetPasswordValidator() let emailAddressValidator = EmailAddressValidator() ...}
Represents the validity of the entire form
Behavior of nil• Most validators allow nil
• SignUpValidator verifies contained inputs are non-nil
Validation
Validation
Set input on corresponding validator
Enable sign-up button
Decorate invalid text fields
For each text field
If sign-up validator OK
Otherwise
Define Clear Responsibilities2
Simplify with immutability3
Design information flow1
Define clear responsibilities2
“Mutability is bad and you should feel bad for using it”
The Internet, probably…
Insight, not dogmaWhy, not how
5
A
B
C
5
A
B
C
5
5
A
B
C
99
99
A
B
C
99
99
A
B
C
99
A
B
C
99 99
99
A
B
C
99 99
99
A
B
C
99 99
99
A
B
C
5
A
B
C
5
A
B
C
5
5
A
B
C
995
5
A
B
C
99
5
5
A
B
C
Swift StructsBest of both worlds
Swift StructsBest of both worlds
Opt-in mutability • mutating keyword
Swift StructsBest of both worlds
Opt-in mutability • mutating keyword
Call-by-value • New copy automatically created when passing struct to another function
55
A
B
C
55
A
B
C
5
5
A
B
C
5
9999
A
B
C
5
9999
A
B
C
5 99
99
A
B
C
UIMotionEffect
UIMotionEffect
Adjust views based on gyroscope data
UIMotionEffect
Adjust views based on gyroscope data
Used to achieve parallax effects
UIMotionEffect
Adjust views based on gyroscope data
Used to achieve parallax effects
Reusable across views
UIMotionEffect
Adjust views based on gyroscope data
Used to achieve parallax effects
Reusable across views
Low-latency requirements
UIMotionEffect
UIMotionEffect
Inputs Outputs
UIMotionEffect
Inputs Outputs
Device pose
UIMotionEffect
Inputs Outputs
Device pose Relative offset for each key path
Inputs Outputs
UIMotionEffectInput deltas
Inputs Outputs
UIMotionEffectInput deltas
Device pose deltas
Inputs Outputs
UIMotionEffectInput deltas
Device pose deltas Relative offset for each key path
Inputs Outputs
UIMotionEffectInput deltas
Previous poses
Device pose deltas Relative offset for each key path
UIMotionEffectAbsolute offsets
Inputs Outputs
UIMotionEffectAbsolute offsets
Inputs Outputs
Device pose
UIMotionEffectAbsolute offsets
Inputs Outputs
Device pose Value for each key path
UIMotionEffectAbsolute offsets
Inputs Outputs
A particular view
Device pose Value for each key path
Simplify with Immutability3
Review
Design Information Flow1
Define Clear Responsibilities2
Simplify with Immutability3
What now?
More Information
Jake Behrens App Frameworks Evangelist behrens@apple.com
Apple Developer Forums http://devforums.apple.com
Related Sessions
• Core iOS Application Architectural Patterns Mission Thursday 9:00AM